1. Field of the Invention
The present invention relates to an instrument illuminating device that is capable of guiding light outputted from a light source toward an object or a portion to be irradiated. In particular, the invention is useful for lighting an instrument of a motor vehicle.
2. Description of the Related Art
A conventional illuminating device of this kind is disclosed in Japanese patent laid-open publication No. 2003-130693. This conventional lighting device is used, for example, to illuminate an indicator of a water temperature meter provided on an instrument panel of a motor vehicle, and it is equipped with a light source for emitting light, a light guide body for guiding the light toward an indicator needle, and an indicator plate having display designed portions, such as scale marks and characters, arranged around a center axis of the indicator needle. The light source is arranged in the vicinity of a spindle of the indicator needle, and the light guide body is arranged between the indicator plate and the light source to receive and guide its light. The light guide body is made of transparent plastic material such as polycarbonate (PC) and polymethylmethacrylate (PMMA), and is formed to have a sector form with a first partially-conic surface for reflecting the light introduced from the light source in an outer radial direction and a second partially-conic surface, which is arranged outwardly in a radial direction and provided with crimps and the like, for reflecting and guiding the light reflected on the first partially-conic surface toward the indicator needle and the display plate so as to illuminate them. The light guide body is arranged and supported between a scale board and a circuit substrate or a reflecting wall part, being associated at its rear surface with the reflecting wall part.
The above conventional illuminating device, however, encounters a problem in that the device cannot uniformly illuminate all parts to be irradiated of the display designed parts thereof, or of the designed parts and a background part in some cases.
In the above conventional illuminating device, the parts to be irradiated, such as the display designed parts or the display designed parts and the background part in some cases, cannot be uniformly illuminated because of the following reasons.
The light guide body is usually formed by using a molding process such as injection molding, where a molded light guide body is ejected from a mold by thrusting ejector pins to the light guide body. This will cause press flaws due to the press force of the ejector pins on a surface of the light guide body, so that these press flaws have optically deleterious effects on guidance, reflection and refraction of the light, consequently deteriorating the uniform illumination of all portions to be irradiated.
Although the above-described document does not disclose a support structure of the light guide body on the scale board, circuit substrate or the reflecting wall part, if pressed portions to be pressed by the ejector pins are provided to project radially outwardly from an outer circumferential portion of the light guide body so as to avoid the optical deleterious effects, guidance, reflection and refraction characteristics of the light at the pressed portions are changed. This also deteriorates the uniform illumination at and near the pressed portions.
It is, therefore, an object of the present invention to provide an illuminating device which overcomes the foregoing drawbacks and can enhance uniform illumination of a part to be irradiated of a light guide body which is integrally formed with a projecting portion which projects from a light guide portion, such as an ejector press portion to be pressed by an ejector pin when the light guide body is ejected from a mold in a forming process thereof, and a coupling portion for coupling with a coupling portion of a support member.